OMG.. My newest obsession. Naked Raku.
Naked – no glaze, what you see is just the clay.
The fired pot is burnished until smooth and then coated in a thick layer of clay slip & glaze before firing again. As this second layer fires, it cracks and crazes in unpredictable patterns. Then when red hot, the pot is dropped into a combustion chamber where it is surrounded by fire and smoke; the smoke enters the cracks in the slip coat and leaves behind black trails and marks on the surface in beautiful smokey patterns.
It took me ages to get it to work. There are lots of sites giving techniques, but my technique was just to keep trying till it worked.
On my next run through I’ll take more pictures and fill this in, but what you want is for it to come out of the combustion chamber (biscuit tin) with the outer skin intact, but cracked. Then because it was made smooth at the start, it’s easy to pick off this outer layer to see what the smoke has done to the surface. Spot, sharp lines, blobs, smears… All lovely and all on a tiny scale!
Ok, full disclosure: I have only had one successful naked raku fire so far. So here goes again, this time with images…
1. Burnish the unfired pot with something hard and smooth 
2. Not sure if you can see, but this fired pot has a sheene. 
3. Homemade slip is 50:50 white stoneware and terracotta. There is a bit of vinegar in there as well. 
4. I waxed the bottoms and dunked them. 
4. Anywhere without the clay mix will go black in the raku. 
5. A good thick coat of slip 
6. When dryish, a coat of glaze to hold it in place.
At this stage the pots have already been bisque fired (so have shrunk). The insides have glaze that needs firing, so as this happens, the outer slip should crack as it shrinks, but stay in place because of the slip.
We will see..
FAIL
OK… So slow down, it’s a multi-stage process:
- Throw pot and leave to dry
- Burnish without breaking!
- Bisque fire
- Interior glaze + fire #2
- Coat in slip. Wait to be touch dry
- Coat in glaze (to hold the slip on a bit).
- Before it dries out too much RAKU fire.
This next test, I’m doing 25 mins - Drop into tin with combustibles